Process of casting heat exchange fins upon a tube



une 10, 1958 E. B. PRlEBE, JR., ETAL 2,837,799

PROCESS 0F CASTING HEAT EXCHANGE FINS UPON A TUBE 3 Sheets-Sheet 1 Original Filed 001;. 20, 1950 5 m T N E V m June 10,1958

E. B. PRIE BE, JR., ETAL PROCESS CF CASTING HEAT EXCHANGE FINS UPON A TUBE 3 Sheets-Sheet 2 Original Filed Oct. 20, 1950 JunelO, 195s E. B. PRIEBEI, JR., "ET AL PROCESS 0F CASTING HEAT EXCHANGE FINS UPON A" TUBE 3 Sheets-Sheet 3 Original Filed Oct. 20, 1950' v "i .fi

SJ R O T N. E v m? PROCESS OF CASTING HEAT EXCHANGE FINS UPON A TUBE Ernest B. Priebe, In, Hudsondale, and Paul Priebe,

Weatherly, Pa., assiguors to Drake Block Co., Inc., a corporation of New York Continuation of abandoned application Serial No. 191,228, October 20, 1950. This application May 23, 1955, Serial No. 510,133

5 Claims. (Cl. 22206) This invention relates to the subject of heat exchange and includes apparatus and tubular circulation elements therefor; such elements or circulators being of a kind wherein a length of conventional preformed metal tubing, such as a boiler tube, of steel, hereinafter designated as the tube part or tube of each circulator element, has applied to and carried by it an exterior surrounding metal addition, hereinafter called the applied formation or added part of the complete heat-exchanging tubular circulation structure. For best heat transmission between the circulating fluid within the tube part and the flowing fluid surrounding the added part or formation of the tubular element, as from exterior gases to interior liquids, or vice versa, or between two liquids or two gases, each circulator or its applied portion is a formation having integral projections or multiple surface-increasing extensions, as in the form of ribs or fins, sometimes called gills, or outstanding lugs or analogous shapes of ample section or thickness; these designs acting to multiply the receiving or transmitting surface area between the tubular circulation element and the exterior fluid.

The present invention conforms with the above general outline and embodies characteristic features of novelty and utility, to be hereinafter further disclosed, directed to the entire tubular circulation element or circulator per se.

As a further branch of the present invention there is disclosed a novel method for producing or manufacturing such product or tubular circulation element, this method consisting of a series of steps performed upon the original or plain tube part, with the aid of certain means or apparatus elements, and such apparatus being adapted to be operated in accordance with such method and being the subject of detail description. 7

In respect to economizer and similar units it has been a problem to secure substantial improvement in efficiency, costs and results over plain boiler tubes, or such tubes with thin longitudinal fins thereon. Among structures that have been tried and used, preformed additions in the form of gilled rings or slidable sleeves were produced, to' be heat-expanded and longitudinally driven upon the boiler tubing, caused to engage each other in line, and cooled to shrink upon the tube. Such systems early proved diflicult in practice, unreliable, inefficient and costly in several respects including the necessity of employing machines to bore and internally ream these sleeve products to afiord as close a fit as possible, together with special apparatus to drive these structures forcibly on to the boiler tubes. So unsatisfactory were these prior systems that it was found necessary toattempt to procure on the market boiler tubes of very close outside tolerance, so as to bring about a uniformly snug fit between the tube and the added elements. Due to prevailing variations in standard boiler tubing much trouble was experienced, requiring the expedient of purchasing the tubes in large quantities, sorting them according to several grades of tolerance and exterior dimensions, changing the operation of the machining of the added sleeves to match the tubes, and using up these tubes grade by grade. This was economically costly and, despite the strong, efforts made, the added preformed elements frequently suffered from poor contact and even substantial looseness, upon the tubes. This looseness not only interfered with the heat transmission, thereby destroying the efiiciency, but it was apt also to result in corrosion, deterioration and even break-down by permitting water such as is commonly used for cleaning to enter into the crevices. This was particularly harmful when agents were present, such as sulphurous gases.

It has also been proposed to cast fins of aluminum, one at a time, on the outside of a steel pipe. The aluminum, as

it solidifies is still quite hot and the pipe is cold, so that the aluminum shrinks on the pipe during the cooling. This creates pressure against the pipe, but there is no union because the melted aluminum will not wet the steel pipe.

The fins are cast, one at a time, to keep the pipe from getting hot because, if the pipe were at the temperature of the aluminum it would shrink with the aluminum and the pressure would not be attained.

.From the above discussion, it will be clear that the efiiciency of heat exchangers has been limited by the imperfect union between the pipe and the fins.

In accordance with this invention the problem is solved in a different manner, by employing metals which are mutually miscible and heating both metals to the point where the liquid metal of the added part will flow into and unite with the surface of the pipe. For example, if two mixable metals of different melting points are heated above the melting point of one of them there is a partial mutual solution at the meeting surfaces which unites or welds the parts together in a single molecular mass.

The principles of the present invention were developed and reduced to practice primarily for use in plants of an engineering character, such as already mentioned above; but similar or modified circulators, within such principles, can be otherwise practically used to advantage, an instance'being the treatment of food liquids or other liquids,

such as fruit juices, to subject them, under controlled temperatures, to desired chemical changes as in the nature 7 of the gradual cooling of the liquids.

In the aspect of the circulator structure, for heat exchange purposes, the invention may be described as follows: It comprises an interior tube part, of a strong metal and, unitary therewith, a surrounding and encasing exterior or added part or formation composed of a preferably different ferrous or other metal. Said tube consists of an extended length of preformed tubing of a strong or wrought metal as steel, typically represented by e tantly superior preferred sectional cast structure of "circulator added formation having practical advantages, wherein is a longitudinal series of short lengths or sections of applied metal, longitudinally'unified, which, may.

be of the order of 10 to 20 inches long, with between 10 and 20 ribs to the sections. These separately produced sections are preferably of two structural types, cast on to the tube in cooperative alternated and contacting sequence along the tube; type 1 section having, projecting longitudinally from each end of its body portion, an underlying toe extension or circular flange and being; .united to the tube for its full length; and type 2, having 1 at each end an overlying lip or ridge extension which is united to the tube and to the underlying toe, with the toe located between the tube and the lip; the lines of integral union between these features being observable in the circulator product, as by dissecting it by sawing out a length or sector. The further details of this preferred structure will be hereinafter disclosed.

The invention consists also in the novel features of method and means employed for the practical production of such tubular circulation elements; and also heatexchange apparatus in which such elements or circulators are employed to advantage for the purposes set forth; all as will be more fully herein disclosed.

In the accompanying drawings of a preferred embodiment of the present invention, the features of illustration include the preferred method of manufacture of the circulator element of the invention, and along therewith described apparatus for carrying out such method, and the product itself in the form of a single circulator element; and as well a practical instance of the utility of the invention, such as the use of many such circulators, namely, in one of the heat-exchange units or chambers of a boiler or other plant.

Fig. 1 is a top plan view showing an instance of the product or circulator element in a partially completed state, as it might exist during the stage of the first heat or cast in the practice of the preferred sectional method of the invention; this figure showing near the lefthand end a casting mold set up for performing an operation for the first cast or stage, while near the righthand end is shown the result of such a casting operation, being the formation designated as type 1, in which, after the casting, the mold is assumed to have been removed. Fig. 2 is a front elevation of the disclosure of Fig. 1, both of these figures showing a part of a first-stage mold omitted to disclose the interior. In so describing Fig. 2, it is to be understood that the word front is used for convenience, there being no essential difference between the front and rear aspects of the apparatus, although the front can be identified in the drawings by the fact that the mold clamp screws happen to be at the front sides of the clamp. Like the terms front and back, the terms left and right are conveniently used de scriptively without intention of limitation thereto, through out this specification. Fig. 3 is a righthand elevation, partly in section on the line 3-3 of Fig. 2, of a device shown also in Fig. 2 for accurate spacing of the first casting operation.

Fig. 4 is a view generally corresponding to Fig. 1, being a top plan view, but with the progress of the operations advanced from the first to the second general stage, the mold being set up for effecting the second or type 2 casting in each one of the gaps or spaces existing between the cast formations, of type 1, of two of the first-stage operations. Fig. 5 is a front elevation of the features disclosed in Fig. 4.

Fig. 6 is a righthand elevation of Figs. 1 and 2 showing the casting equipment as set up for the first stage of operation of applying added structure of type 1 to the tube. Fig. 7 is a similar righthand elevation, also showing the parts in first-stage position, but this figure being partially in transverse vertical section on the section line 7-7 of Fig. 2.

Fig. 8 pertains to the second heat or cast, being a righthand partial' elevation and a partial section taken on the section line 3-8 of Fig. 5.

Fig. 9 is a diagrammatic view showing the principle of utilizing a bank of the circulator tubes hereof, arranged within a heat-exchange chamber, as of an economizer unit, adapted for coupling to exterior passages.

Fig. 10 is a front elevation, broken away centrally for abridgement of the drawing, and shown largely in central section, of a circulator in accordance with the invention; and the righthand end of this figure in dotted lines-presenting additional disclosure of a special supplemental casting means for producing on each. tube a 4 tube-sheet closure-ring or plug, as will be further described, this special showing to be considered in connection with Fig. 11. Fig. 11 is an exploded perspective view of one of the like halves, either front or back, of the special mold preferred for the casting of metal on to the tube to constitute the closure ring or plug shown in Figs. 4 and 5 and more especially in Fig. 10.

Fig. 12 is a transverse sectional view of the lapping structure of and relation between two adjacent applied formations, being taken on the section line 12-12 of Fig. 13. Fig. 13 shows a detail of the adjoining ends of two added formations, of types 1 and 2 respectively, already referred to, bringing out the manner of uniting and interlocking thereof with each other and with the interior tube. Fig. 14 is a central sectional view, partly similar to Fig. 13 but on a larger scale, and showing the character of the intimate uniting of the contiguous castiron parts and the interior tube at one of the successive joints or points of union involved in the use of the interlocking 2-stage casting-on system of the invention.

Referring specifically to the drawings, the manufactured product or circulator 20 is shown in Fig. 10 in its full extent from end to end excepting for abridgement of the drawing around the middle of the figure. The use of a bank of such circulators, as in an economizer, is diagrammatically indicated in the small-scale view Fig. 9, to be further referred to. The circulator is preferably formed with a return bend 21 through which, by suitable means 22, as welding, a vertical group of circulators may be interconnected in series or tandem, as indicated in Figs. 9 and 10. The weld may be cut for removing a circulator.

It is to be understood that the entire bank of tubular circulators 20, comprising e. g. twenty groups of e. g. ten circulators superposed in each group, is suitably supported within an enclosed space. Using a common mode of suspending the circulators there is shown at the left end of Fig. 10 at a tube sheet or wall 24 formed with numerous relatively small holes to receive and hold snugly the lefthand ends of the tube portions of the circulators. At the righthand end is an analogous tube sheet 25 formed with larger holes or apertures to receive and support the righthand ends of the tubes which, at this point, are provided with enlarging rings, collars or closure plugs to be further described. As appears in Fig. 9 a heat-exchange chamber 26 is represented by the showing of some of its bounding walls, one of which is the righthand tube sheet 25; and this diagram indicating that a plurality or bank of interconnected circulators are arranged in parallel superposition within this, the operating chamber 26 of the economizer or other apparatus unit. To the right of the righthand tube sheet 25, and spaced endwisc well away therefrom is a housing wall 27 which, along with the tube sheet wall and other adjacent walls define a vestibule or accessible space 28 enclosing the circulator portions which extend beyond the tube sheet. For the purpose of detachment, replacement or inspection of the individual circulators, access is provided by reason of the ready removability of the housing wall 27, or at least the provision of detachable doors or panels therein.

In its general aspects each circulator 20, whether type 1 or 2, comprises its central tube part 30 of steel, combined in a special way with an added part 32, the latter being a formation composed of a cast metal, preferably castiron, as previously set' forth. This added formation will at first be described in a general way, with reference to the top, front and right-end views of Figs. l2, 4-5 and 68, without distinction between the two types of formation. In both cases the formation 32, applied to the central tube, consists of the annular body 34 having the outstanding ribs 35. It is highly advisable for best heat conducting results that these portions'34 and 36 be not thin or of slender character like sheet metal fins, but rather annular portions of good heat-transmitting extends the full heat-exchange length of the tube, and

it consists of'the annular body 34, integrally united with the interior tube and formed with the extensions or annular ribs 36 outstanding from the body of a surface extent to increase greatly the heat transfer area of the circulator. See Figs. l2 and 5-6.

The combination of this tube part 35) and these added parts 32, 34 and 36, in this typical structure of the invention, embodies the principle of applying the aforesaid formation, the body plus the ribs thereof, as a nonpreformed application to the tube. This conception is herein carried out by means of the simultaneous applying and forming of the added parts in situ, they being pro- I duced in their proper place in the circulator by casting the added formation directly upon the inner or central tube.

Irregularities'in the surface of the tube are without significance but to insure the union of the castiron it is important that the tube surface be thoroughly precleaned, preferably by sand blasting and cleansing, so that any imperfections, due to the presence of areas or spots of rust or millscale or other impurities, can not cause impairment in the casting-on operation.

Passing from the general to the specific principles involved, the circulator tube part 30 is without difference, but it carries a series of short lengths or sections of applied metal, laid in longitudinal alinement and unified, end to end; each of these sections having the described general formation of the added part 32 directly upon the tube, and itself consisting of its annular elongated body 34 formed with its rib extensions 36. Instead, however, of these sections being duplications of uniform formation throughout, they are, in the preferred specific structure, of slightly but importantly different structure, designated in Figs. to 14 as added formations of structural type 1 composed of body 38 with ribs 39, and type.

2 composed of body 40 with ribs 41. In other words the general reference numbers 32, 34 and 36 of Figs. 1 and 8 are replaced by 38-39 for type 1 and 40-41 for type 2 in Figs. 10 to 14. The body portion 38 and 4t) differ in a complementary manner in their end constructions. 7

The two types of added formation are cast and carried upon the central tube in alternated and contacting sequence and abutment along the length of the tube, as appears best in Fig. 10, but indicated also in Figs. 1 and 2, in the sense that spaced-apart type 1 formations have been produced or are about to be produced with gaps therebetween, and Figs. 4 and 5 wherein, after the spaced type 1 formations have been completed, the type 2 formations are cast or about to be cast in locations to occupy the gaps between the type 1 formations. As the drawing shows, each type 1 formation has its body formed in the same manner at both of its ends i. c. with an extended toe united with the central tube surface; and the same with type 2 body and its lip.

The complementary differences between type 1 and structions of the body portions 38 and 40 and are best indicated in Fig. 10 and, on larger scales in Figs. 12-14. Thus the integral formation at each end of the added body 38 of the type 1 formation comprises an endwise extension 42, in the nature of a collar, somewhat thicker than the rest of the body, from which collar in turn projects endwise a shallow annular extension, designated for convenience as a toe 43, somewhat thinner than the rest of the body. These parts, the body and extensions,

, type 2 added structures reside principally in the end conare united integrally and the inner tube, the toe extension 43, in the nature of a .circular flange, servingas the underlying part in the joint or unification of the end of each type 1 formation 3839 with the adjacent end of the type 2 formation 49-41. The type 2 body 40 has an overlying endwise extension 45 for convenience called a lip, is also in the nature of a flange. This toeand-lip relation between the added sectional formations, or their bodies 38 and 40, and the union of these parts with the interior tube, are brought about by applying, in a first production stage, the formation 3839 integrally upon the tube, namely, by there casting it of the illustrated structure in accordance with the correspondingly formed mold; and in a second stage similarly casting the type 2 added formation having the body 40, with its overlying lip 45 applied upon the outer surface of the toe 43, affording a-strong and tight or integral uniting of the two formation types. The casting of the end of the type 1 formation upon the tube renders these integral, including the toe 43, and the following interlocking casting of the type 2 formation, with lip 45 upon toe 43, affords integral uniting of the two types to each other as well as to the interior tube, the toe of the type 1 formation becoming an intermediate locking member extending endwise between the tube and the lip.

Fig. 14 indicates by interlaced or lapping cross hatching the intimacy of united contact at each joint between types 1 and 2 of applied formation, and between these and the tube the portions so drawn showing the places of more special tight interconnection or integrally approaching that of a welded joint.

In Fig. 10 and others the lefthand end of the leftmost type 1 formation 38-39 is shown as terminating with the collar 42, the unnecessary toe extension 43 being omitted, this giving a better abutment of 42 against the tube-sheet wall 24 and saving slightly in total length of the added body 38. instead however of casting this lefthand formation in a third-type, the toe may be left on, as with other type 1 ends; or the casting mold may be modified by filling its toe space with supplemental molding material.

Having'described the cast-on configuration of each added section, of either type, there has been determined the interior configuration of the mold and the casting spaces, which in turn are predetermined by the use of a corresponding pattern for making the mold.

Before entering into a description and further explanation of the method followed by the present invention and the casting means used therein, certain general matters will be referred to. A main supporting part for each of a number of sets of apparatus is a working base or low table 50, which may be in the form of a channel iron having its flanges resting on the foundry floor and installed with its supporting web level and even, the working surface being for example about or over 20 feet in length and of a width somewhat under 2 feet. It not merely supports each of the many molds of a series, and the front and back halves thereof, but holds these at a uniform level while permitting them to be slid toward and from each other in closing and reopening the bisected mold. A mold-half registering or alining means 60 is elsewhere described, as well as clamp means TS- 77 for securing the mold tightly closed during the casting.

Various general foundry expedients may be used, in-

. eluding jigs as needed. For example the drawings show a number of high seats, 'angle blocks or chairs 51 arranged on the table 50 in lengthwise series and facing alternately to the front and back, thus to give definite straight and level direct support, positioning and elevation to the central tube throughout its length, during the first cast; and at the projecting tube ends during the second cast. Other seats comprise low blocks or stools 52, which may be of wedge form, adapted during the second cast to take the weight of and to support the circulator structure at points beneath the tips of the formed ribs 36 of the first heat. In these ways there are ensured definite axial elevational height and straightness of tube, at suitable intervals, during first and second casting operations.

A subordinate feature is a temporary gage means 54 used before and during the setting up of the first-heat molds to predetermine accurately the spacing between the successive alternated first-cast formations 32. See Figs. l3. This device consists in a longitudinal gage piece of correct length adapted to be set between two successive first-heat molds to space them so that the resulting first-cast formations will be spaced along the tube with gaps of the exact length to accommodate the the second-heat formations. The gage piece 54 is shown as an arcuate piece, or sleeve segment, preferably overlying, straddling and supported upon the tube 3%} in the manner of a saddle; this element to be removed after the first-heat molds have been set up, thereby to permit the second casting mold 58, 59 to be fitted into the gap or space between the first-casting formations as determined by this gaging saddle member. On the removal of the saddle gages, the first-heat molds may be plastered with fireclay, asbestos cement or like refractory to close up and stop all visible cracks and crevices, in advance of the actual casting in these molds, to preclude the escape of molten metal.

The molds in which the cast formations are produced, simultaneously shaped and applied, with correct spacing, to the tube 30, are to be of type 1 for the first series of casting operations and of type 2 for the second series of operations; and in either case the mold is of generally upright oblong character, bisected into oblong front halves 56 and back halves 57 for type 1 sections; and front halves 58 and back halves 59 for type 2. The mold half of each type sets upright firmly on the table and the two are brought together from in front and behind the tube Stl in assembling the mold to surround snugly the tube. For type 1 the mold is best illustrated in Figs. 1, 2, 6 and 7; and for type 2 Figs. 4, and 8. Figs. 10 and 11 together show also a special third-type mold structure for producing in the second casting a closure ring or plug of enlarged diameter at the righthand end of the circulator for the special purpose, to be further described, of engaging that end of the final circulator upon the righthand tube sheet 25. The molds are preferably of prebaked sand with conventional ingredients, as a binder, which may be of a phenol resin.

In considering any of these mold forms, of either type, it is to be understood that the interior tube 30 constitutes a part of the mold, against the outer surface of which the molten iron is directly applied and which determines the shape of the mold cavity at this central location, the cast metal becoming integral with the tube, but the latter requiring no preheating, as complete fuse welding is not essential to the intimate, integral uniting of the tube and the applied formation of body and ribs.

The mold spaces in general comprise a primary or main mold space 61 representing the annular body 34 of the applied formation, which space is uninterrupted lengthwise and extends outwardly between the interior tube and the line of mold rib spaces 62. In turn, these rib spaces 62, which are annular, extend from the body space outwardly, and each rib space extends between two of a series of core-like annular inward extensions or flanges 64 of the mold, these rib spaces extending between said mold extensions 64, outwardly to the gates 69 through which the molten metal is fed downwardly to all of the mold spaces. This description substantially covers the mold casting spaces, with the exception that it is to be understood in regard to the lengthwise extending collar 42 and toe 43 of each type 1 formation that these are provided for by corresponding endwise extensions 65, see Fig. 2, in the casting space of each mold; and as to the lip 45 that it is cast in the endwise space extension 66, see Fig. 5.

Referring next to the flow of the molten metal, as from a ladle, by way of suitable passages provided in each mold; the first such passage includes the pouring hole 67. This is a top and central feature in both lengthwise and sidewise senses and therefore is bisected, in the same central plane as the mold is bisected into near and far registering halves. The pouring hole or inlet recess 67 is in the nature of a relatively small and shallow basin, as seen in Figs. 1-2 and 4-8, and it receives the molten material and delivers it to the next passage element 68 in the nature of a trough, open channel or gutter. The pouring hole is fed with molten iron in a conventional way, the poured metal advancing onward through the guiding elements and casting spaces to fill the general mold cavity 6162 and other recesses of the mold. The trough or gutter 68 extends longitudinally and substantially horizontally, constituting a distributor or manifold, first carrying the poured metal to where it may flow from the trough at several points and pass downwardly by a series of short downtakes 69, which may be considered as gates or entrances connecting the trough directly with the casting spaces 61, 62 etc. therebelow.

The interior volume of the mold and the molten iron supplied to the mold must be sufiicient and of such a temperature as to heat that portion of the pipe which is within the mold up to substantially a welding heat, that is, to the point where the molten castiron unites and substantially welds with the surface of the pipe so that they may solidify into a common mass at the surface joining.

In any case, the length of the mold will be such as to cause the molten metal to heat the tube substantially to uniting temperature without melting it.

At the same time, care must be taken that the iron is not admitted to the mold at a sufficiently high temperature to'melt a hole through the pipe and is so distributed in pouring as to flow into all parts of the mold without concentrating too much at one point.

As will be understood, enough iron will be supplied to fill the casting spaces and preferably to fill as well the short connecting downtakes and, at least partly, the longitudinal trough, extending upwardly initially even into the pouring hole; so that when the poured molten iron hardens or freezes there will exist the main casting or formation applied upon the tube, and extending upwardly from the top of the added formation a projecting sprue or sprues of excess metal. The latter, at a suitable stage in the cooling of the casting, may be removed by knocking it off and thus breaking it from the main casting at or near the gate line, whereat the flow space is of minimum section; thus isolating the casting itself, for finishing treatment if desired. It is found with this invention that no air venting channels need to be provided. The manner of distributing the metal, from the center inlet hole endwise in both directions, in the trough and from the trough to the line of numerous connecting gates, is such that air within the casting space tends to flow endwise from the center of the mold, thus to rise in the casting space and escape by way of a few of the gates at or near each end of the gate series. The air is thus relieved and crowded out of the mold while the molten metal flows downwardly into the mold and longitudinally from the center toward the ends and, throughout the length of the mold, upwardly to force out the air near the ends, as described, and to fill up the rib-casting spaces between the row of flanges 6 3- which determine the size and shape of the ribs of the formation beins cast upon the central tube. Auxiliary factors may be employed to aid the avoidance of trapping of air within the mold, such as the plan of constructing the mold of a high quality prebaked material including in mixture with the sand of a special binder material of any known kind which tends to form and maintain a use ful degree of porosity throughout the hard body of the sand.

The step of setting up each bisected mold, of either type 1 or 2, has been generally indicated. The two moldhalves are identical, so that by turning through one of them the two halves face each other in readiness for futual engagement, for example, in the case of Figs. 1 and 2 the front mold-half 56 of type 1 and the complementary similar back half 57 and similarly in the case of the front and back halves 58 and 59 of type 2, Figs. 4 and 5. The two half-molds, in either case, standing on the table in their proper posture, face to face, with the tube 30 between them are readily slid toward each other upon the table 50'into proper mutual engagement. The tube in each case stands poised centrally, supported by the seats or chairs 51 and/ or 52.

In this condition, in the case of the type 1 mold, its end walls 60 have relatively small circular central holes, of a size or diameter to fit snugly and hug the interior tube, the combination of the end walls and the tube thus providing a closure of the mold at each end. By the mold end walls is meant the end portion beyond the last of the rib spaces 63 at each end; this applying to molds of either type. The type 1 molds have been correctly spaced by the gage 54 as already described, see Figs. 1, 2, 6 and 7. The tube and the first mold 56, 57 are thus mutually centralized, but not yet in readiness for casting.

Later, in effecting the casting of the type 2 series of formations, the arrangement is largely similar to that just described for type 1, but the type 2 molds 58, 59 are seen, as in Figs. 4, and 8, to have their end walls 61'formed with holes that are of considerably larger diameter than that of the tube, and larger therefore than the end wall holes of type 1, and indeed of sufficient diameter of hole to overreach and fit snugly,'at each end, upon the endwise projecting collars 42 previously cast in the first casting stage. By this arrangement, during the second casting, the casting space of the type 2 mold 58, 59 is bounded internally not merely by the tube 30 itself, but by the underreaching metal parts of the already cast formation of type 1, these type 1 parts, exposed to the second stage casting, being the collar 42 and the toe 43 projecting endwise from the body 38 of each end of the type 1 formation. This set-up casting arrangement of type 2, shown in Figs. 4, 5 and 8 yields the result which is shown in Fig. 10 and elaboratedin Figs. l2-l4 as previously described. During these second stage operations the circulator under construction may be maintained in its centralized position by the high chairs 51, but only at the tube ends where they extend beyond the added formations, while for additional support it is desirable to use the low seats or stools 52 serving to support the tube against sagging, during the second casting stage by the position of these low chairs or blocks beneath the series of cast ribs 36, produced during the first stage; see particularly Figs. 5 and 8, the latter indicating that the support or block 52 may have a wedging top surface thereby to afford firm and rigid support to the tube and its carried formations during the second casting and cooling. It is to be understood that the second casting does not take place until the first cast formations have hardened and thefirst moldscleared away, see Figs. 4 and 5, for setting up the second molds. I

As an adjunct of convenience in the setting up of the pair of mold halves of either type 1 or type 2 there is shown a registering device 71, indicated generally in Fig. 7. The preferred device is of the lug-and-recess type. While one such device may be used, centrally of the length of the mold, it is preferred to employ two thereof at symmetrically spaced points on each mold, preferably one near each of the two ends of each half of the mold and near to the bottomof each inner face. An effective means consists of a device having a lug 72 on one mold half engageable with a recess 73 on the other half near one end, and the reverse thereof at the other end; these being adapted to engage reasonably accurately, witha slight loose endwise play to permit under visual inspection a supplemental top view and manual checking and adjusting of registry. Fig. 2 shows such a recess 73 near the righthand end of the back mold, the lug 72 near the lefthand end thereof not appearing on this figure; but Fig. 5 showing the lefthand lug 72 in full lines, and near the righthand end the recess 73 in dotted lines. The registering means so indicated aids in the accurate setting up of the mold halves in their correct positions relative to each other and to the central tube; but the setting up is not considered complete without the tight securing of the mold parts in these positions by a suitable mechanical" means exerting squeezing pressure to unify each set-up mold in a safe manner for casting molten metal therein.

For the purpose of securing snugly and safely the two mold halves for casting purposes it is preferred to make use of a clamping means 75 of any conventional type, such as a screw-operated device, herein available for the molds of either the first or second type or for the closure plug type of Figs. 10 and 11. There is specifically shown an inverted U-clamp '75, adapted to overreach the top of the combined mold, with drop legs adjacent to the mold front and back faces and adapted to apply inward pressure at both faces, thus forcing and maintaining the mold halves in tight relation, avoiding displacement or spreading of the mold halves. The described clamp may be of the type using screw action for exerting clamping pressure, and front and back screws may be employed, although a single or front screw 76 is sufficient, as shown. See Figs.'1-2, 4-5 and 6-8. It is desirable to avoid damage to the mold parts by the clamping pressure thereon,

and for this purpose the pressure is rendered indirect by inserting, in advance of positioning the clamp, a pressure plate 77 at each of the front and back faces of the mold, so that when the clamping pressure is applied, in i a symmetrically opposite way, the pressure is received by these plates 77 and thus distributed over substantially the full areas of the mold halves. There may be a single clamp screw 76 on each leg of each clamp, or two of them, upper and lower, as shown, for more effective clamping pressure. The plates 77 may be allowed to rest down upon the working table 50 before the setting up of the mold is completed by the application and tightening of the clamp.

Reference has been made to the optional formation upon the central tube 30, near its righthand end, of an applied addition 80, which has been designated a closure plug or ring, of outside diameterv slightly greater than that of the rib extensions 36, and such as to fit into and close the relatively large holes in the righthand tube sheet 25. Such an integral enlargement or plug, applied after the type 1 formations have been completed, is desirable as a practical way of mounting the righthand ends of the circulators in place in the heat-exchange chamber, with adaptability for endwise removal of circulators at that end and replacement thereof. Such a closure plug 80 cast on to the tube 30 is shown in the top view Fig. 4 and the front elevation Fig. 5; its sectional structure is elaborated in Fig. 10, and an appropriate mold for applying the plug structure to the central tube is shown or indicated in Fig. 10 and in the exploded perspective view of Fig. 11.

The molds and methods herein employed for casting in situ the formations 32 of body and rib portions, in volving a first stage or heat for the spaced sectional type 1 formations, followed later by a second heat for casting the type 2 formations, have already been disclosed in full; and the supplemental formation of the closure plug 80 is such that it may be attended to in the same second stage or heat as the type 2 formations by pouring molten metal into all these molds. Theplug 80 is in a sense a third type, applied integrally upon the tube in such a way as to become integral also with the body portion 34 of the righthand end structure of the most righthand type 1 formation, which latter includes at its righthand end an extension collar 42 and an underlying toe 43, as best seen in Figs. 1, 2 10and 13. The plug takes the form of an annular enlargement or cylinder. Its integral union with the tube is brought about by casting the plug dir ctly upon the tube, while the mold, to be described, has a main casting space 83, and also a lefthand casting space extension 84, for producing on the added casting structure a lip S1 abutting against the collar 42 of the adjacent type 1 formation, with its lip overlying the toe 43 of the type 1 formation; so that at the meeting place the parts 34), 42, 43 and 81 become integrally united.

The righthand circular face of each plug formation 89, fitting closely within the apertures of the tube sheet 25, may be flush therewith at the righthand outer side; so that when the circulator is in practical use these parts 25 and 89 may be kept sealed by spreading a suitable coating, as asbestos cement, over the exposed outer face of the tube sheet, covering to a substantial depth at the same time the flush faces of all of the closure plugs, not merely providing a simple sealing means for the entire tube sheet and plug series, but substantially locking them together, which is aided by the presence in the face of the plug of an annular groove 82 adapted to receive some of the sealing composition. This tube-sheet arrangement and a packed arrangement at the tube sheet 24 minimize escape of gases flowing through the chamber 26.

The cast-on closure plug or enlargement 80 may be formed by a casting means or mold of the character shown in broken lines in Fig. 10, this being a bisected mold as better illustrated in Fig. 11, half in full lines and half in dotted lines. The mold is composed of a bisected main mold member 85 at the left and at the right a bisected separate member or closing wall piece 91; these four mold pieces being mutually assembled in a way to surround closely the tube 3% at the righthand part of the mold, but with a larger aperture at the lefthand wall, of member 85, to surround and closely fit the co lar 42 adjacently to the toe 43 of the adjacent type 1 formation.

In considering the perspective view of Fig. 11 it must be taken into account that for clarity of disclosure the exploded parts of Fig. ll are shown, not as they will stand when set up on the table, but in an overtilted posture, requiring the parts shown in this view to be considered as retilted frontward, through 90, thereby to bring the pouring hole to the top where it should be. With this in mind, the bisected main mold member 85, defining the main cavity or molding space 83, consists of a front half 86 and a rear half 87 At the top side, between these bisected halves is the bisected pouring hole 88, which delivers directly into the annular cavity defined by the central tube and the described mold parts, as well as into contact with the contiguous parts of the type 1 formation. The shape of the bisected lefthand end wall 89 of the mold is such as to define the plug lip extension iii, which becomes cast directly in contact with the body extensions 42 and 43 of the type 1 structure. In other words the bisected hole 99, for casting purposes, engages snugly over the collar 42 and therefore is larger in diameter than the tube 36, while providing a tight fit against escape of molten metal at that point, leaving a space outwards of the toe 43 to receive the metal to form the lip 8 The separate or righthand mold member 91 of the plug mold is in the nature of a closing piece or end wall, which is bisected for setting up purposes and which fits snugly the tube 34 so as to prevent escape of molten metal through this righthand mold member 91. The bisected mold member 91 comprises a front half 92 and a rear half 93, with the tube-size hole 94 between them.

The setting up of the mold 85, 91 is readily effected by placing upright the front half-members 36 and 92 facing the rear half members 37 93, all facing the tube 36, and sliding all these members toward the tube to surround it, in a longitudinal position as close as possible to the body 38 of the type 1 formation at the left. The right'nand closing wall members 92 and 93 are moved I leftward into snug engagement with the main mold members 86 and 87, and these into engagement with the type 1 formation. Registering of the main or lefthand mold member 85 and the separate righthand member 91 to each other is provided for by means of upper and lower lugs or projections as, formed on rightwardly extending upright wings on narrow flanges 97 at the front and back walls of each of the half molds 86 and 87, and complementary upper and lower recesses 98 formed in each of the half members or walls 92 and 93. When the mold is set up the mating righthand halves 92 and 93 together occupy and fill the narrow upright space between the wings 97, 97, thus registering the four mold parts in that sense as well as by the engagement of the registering lugs 96 and recesses 98. In other words, the registering devices 96, 98 engage when the assembled half members 92 and 93 are fitted into the space between the front and back wall extensions or wings of the assembled half members 86 and $7. Of course, during the setting up, the front and back mold members embrace and surround the central tube 50, which thus partakes in the casting operation.

Clamp means analogous to the clampers 75 and upper and lower pressure screws 76, already described, may be used to hold the four portions of the mold 85, 91, securely and tightly in place during casting. Such a clamp 75 is indicated in Fig. 10, but set at an incline to provide an additional function, with screws 76 to tighten the clamp, and with interposed protective pressure plates standing against the front and back sides of the mold; thus preventing separation and escape of metal in that direction during casting; while, for securing the end wall pieces 92 and 93 to the main mold member, wedging plates 99 are placed against these mold wall members 92 and 93, and are held in place by supplemental clamp screws 100.

Referring further to the economizer or other unit con taining the circulator elements of this invention, and with reference to Figs. 9 and 10, it is to be understood that, in each group of circulators 2t), when their righthand ends are interconnected in series as by the return bend 22, supported by the plugs and the righthand tube sheet 25, the far or lefthand ends of the circulators may be similarly included in the series arrangement, excepting as to the terminal ones thereof, which usually will reach beyond the tube sheet 24 in the form of two exterior tube ends, which in turn may have connections extending to headers or other couplings forming general parts of the equipment in which the units are used. For removal and replacement of circulators found to be defective the usual procedure would be to sever, or burn by blowtorch, at the weld point 22, the return bend 21, with similar cutting-01f at the far left end, thus disconnecting the defective circulator from the circuit. On account of the larger holes of the tube sheet 25, the circulator may be extracted rightwardly and either repaired or replaced by a similar one, inserted from the righthand end of the unit, slid into place and then reconnected by welding the inserted circulator to restore it to circulation in the group to which it pertains.

It will observed from Figs. 5, 10 and 13 that at each juncture between formations of the first and second type, or the body portions 38 and 40 thereof respectively, the space between the two ribs adjacent to this joint is somewhat greater than the normal lengthwise spacing, and that this is due to the presence, at each end of the type 1 formation or body, of the integral collar 42. This arrangement is no appreciable detriment but on the contrary involves a distinct advantage. The collar 42 is substantially the end feature of the type 1 formation body 38, and forms the base from which the underlying toe projects somewhat further for cooperation with the oppositely extending projection or lip 45 of the type 2 body. The advantage lies in the fact that when the type 2 formation is being cast each of the ends 61 of the type 2 mold overlie the collar 42; this cooperation of the end parts of the respective molds and castings ensuring a snug and tight fit between the type 1 casting already formed and the subsequently applied type 2 formation, as is best seen in Figs. 4 and 5 wherein the mold end 61 13 surrounds the collar 42, the end of said collar and its extension toe cooperating to define the casting space 66 (Fig. which represents th: end metal of the type 2 formation, being the lip 45 extending from the body 40 and overlying the toe 43.

A modification in method and product was devised to dispense with the need of two different types of applied formation, requiring two heats and two distinct steps of production. As disclosed in the drawings each type 1 formation, except the first terminal one, is formed with the type 1 of interlocking structure of toe and lip; that is, both ends of each type 1 formation are formed with receiving toes, requiring the spacing apart of these formations, during the first heat, leaving it to the second heat to fill these spaces by the casting on of the type 2 formations, each with an overlying lip at each end. Instead of the arrangement so described, a hybrid type may be employed, the first or right end of which is of the character of the type 1 section, that is, with the underlying toe extending longitudinally toward the right, this to be like the structure already shown at each end of each type 1 section, The second or lefthand end is to be, under the modification, of. the type 2 character, that is, ending with its longitudinal overlying lip, extending to the left, adjacent to the righthand end of the type 1 formation, as in Figs, 10, 13 and others. In other words the illustrated formations of type 1 have at the two ends thereof a toe and second toe; while type 2 have a lip and a second lip; the hybrid structure however having first a toe extending from the righthand end of the section and the lip extending from the lefthand end. With a continuous series of formations, thus produced, the whole method can be carried out with a substantially continuous operation, in a single stage, taking care of the entire series of body-and-rib formations. Thus, any one of the hybrid formations, when cast on to the tube may be allowed to solidify, the mold being then removed and thereupon a duplicate of said section may be cast on with its lefthand lip overlying the righthand toe of the preceding section; and so on from section to section.

Among other mechanical and method features which are subject to modification within the scope of the in vention is the following: Thus, referring to the 2-stage method of producing the circulator hereof, referring particularly to Figs. and 13, the interlocking joint between contiguous formations of the first and second types, the interlocking structures of the first and second types are provided by interposing a collar 42 between the nearby ribs 39 and 41 outstanding from the body portions of these adjacent sections or formations; the uniting being done by applying the first type of formation upon the tube, with its underlying toe 43 and subsequently casting on the type 2 section, with an overlying lip 45 that becomes integrally united with the toe. For the purpose of setting up the type 2 mold for these operations,.the collar 42 provides a seat receiving the left end wall 61 of the type 2 section, as shown in Fig. 5. The result is that, due to the collar, an excessive'spacing between the adjacent ribs of the two sections is caused, as appears in Figs. 10 and 13, wherein each of the interlocking parts, toe and lip, are of substantially oblong form. This may be modified by omitting the collar 42 and instead, providing at this point, an additional rib 39 of type 1, which preferably extends outwardly to the same diameter as the other ribs but. is formed with a flat instead of a rounded circumference, which may be the part of the type 1 section contacted by the end wall of the type 2 mold, for closing such mold at this point. The toe and lip features need not be oblong for these purposes, but may be beveled off, so long as the lip remains overlying upon the toe.

This application is a continuation of our prior application, Serial No. 191,228 for Heat Exchange Apparatus and Tubular Circulator Elezni-nts Therefor, filed October 20, 1950, now abandoned.

What is claimed is:

1. A process of forming a heat dissipating member which comprises enclosing a length of a steel tube with a mold having inwardly-projecting ribs thereon, and forming a casting of castiron within said mold, the length of the mold being such as to cause the molten metal to heat the surface of the tube to uniting temperature without softening the tube, whereby the cast metal is united to the tube surface.

2. A process of forming a heat dissipating member which comprises enclosing a length of a steel tube with a mold having annular inwardly-projecting ribs thereon, and forming a casting of castiron within said mold, the length of the mold being such as to cause the molten metal to heat the surface of the tube to uniting temperature without softening the tube, and in which the molten metal is admitted to the mold at distributed points along its length, whereby the cast metal is united to the tube surface.

3. A process of forming a heat dissipating member which comprises enclosing a length of a steel tube with a mold having annular inwardly-projecting ribs thereon,

and forming a casting of castiron within said mold, the

length of the mold being such as to cause the molten metal to heat the surface of the tube to uniting temperature without softening the tube, whereby the cast metal is united to the tube surface, and thereafter enclosing said tube with a second mold for forming on said tube a similar casting adjoining said first-mentioned casting and then forming such adjoining casting within said mold.

4. A process of forming a heat dissipating member which comprises enclosing a length of a steel tube with a mold having annular inwardly-projecting ribs thereon, and forming a casting of castiron within said mold, the length of the mold being such as to cause the molten metal to heat the surface of the tube to uniting temperature without softening the tube, whereby the cast metal is united to the tube surface, and thereafter enclosing said tube with a second mold for forming on said tube a similar casting adjoining said first-mentioned casting, and then forming such adjoining casting with said mold, said castings having interengaging flanges.

5. A process of forming a heat dissipating member which comprises enclosing a length of a steel'tube with a mold having annular inwardly-projecting ribs thereon and forming a casting of cast iron within said mold,

the length of the mold being such as to cause the molten metal to heat the surface of the tube to uniting temperature without softening the tube, whereby the cast metal is united to the tube surface, applying a similar mold to another portion of said tube spaced from said first casting by the length of a casting, and forming a similar casting within said second mold, and thereafter applying a similar mold to the intermediate portion of the tube and forming thereon a third casting connecting the first two castings together.

References Cited in the file of this patent UNITED STATES PATENTS 102,078 Backus Apr. 19, 1870 881,191 MacLachlan Mar. 10, 1908 1,565,304 Bell Dec. 15, 1925 1,944,744 Kuhlke Jan. 23, 1934 2,201,024 Brown May 14, 1940 

